Critical Race Condition in Apache HTTP Server Enables Remote Code Execution

Approximately 64% of cloud environments currently host resources vulnerable to CVE-2026-119618, a critical race condition in the Apache HTTP Server's HTTP/2 module (mod_http2). This flaw allows remote, unauthenticated attackers to trigger heap memory corruption, potentially granting them the ability to execute arbitrary commands with the same privileges as the web server process.

This screenshot provides a clear reference for the specific versions of Apache HTTP Server (2.4.55 through 2.4.70) and mod_h2 builds that are affected by the vulnerability.

Mechanism of the Heap Corruption

The vulnerability, identified as CVE-2026-119618, stems from a concurrent execution race condition. When the mod_http2 module handles shared resources, the assign_headers() function fails to properly synchronize threads, leading to memory corruption.

Chart drawn by HN Digest from figures reported by wiz.io; values are shown as written in the source.

By exploiting this lack of synchronization, an attacker can corrupt the heap memory of the hosting server. This memory corruption is a high-severity flaw because it serves as a direct path to Remote Code Execution (RCE).

“If successfully exploited, a remote, unauthenticated attacker can corrupt heap memory to achieve arbitrary code execution (RCE).”

— Critical RCE Vulnerability in Apache HTTP Server: Everything You Need To Know | Wiz Blog

Cloud Environment Exposure

Data from Wiz suggests significant risk for cloud-based infrastructure. Because a compromised Apache instance can serve as an entry point, attackers may use the breach to move laterally into adjacent microservices or access cloud metadata endpoints.

The scale of the issue is notable: while 64% of cloud environments are vulnerable, more than half of those instances are publicly accessible, increasing the likelihood of successful exploitation by threat actors.

Remediation and Mitigation Steps

The primary fix involves upgrading the Apache HTTP Server to version 2.4.71 or newer. For those managing standalone mod_h2 builds from GitHub, the module must be updated to a version newer than 2.0.42.

If an immediate upgrade is not feasible, security teams can mitigate the risk by disabling HTTP/2 support entirely. This is achieved by editing the configuration file (e.g., httpd.conf) to remove h2 and h2c references, restricting the server to HTTP/1.1 only.